It is known that polyalkenyl aromatic polymers such as polystyrene and styrene-acrylonitrile polymers (SAN) can have their toughness properties such as impact strength, elongation and overall toughness improved by incorporating commercial diene rubbers having a molecular weight of 30,000 to 250,000 in amounts of 2 to 36 percent by weight. HIPS and ABS are used commercially as tough engineering plastics for molding and sheet products having great commercial utility.
The engineering properties of rubber reinforced HIPS and ABS polymeric polyblends need further improvement to meet the ever increasing industrial requirements of such plastics. In particular, the elongation at fail without loss of tensile strength has been found to be a critical property of toughness that has been only adequate in known HIPS and ABS polyblends.
It is known to add lubricants such as mineral oil and waxes to improve the elongation at fail of such polyblends. However, such additives lower the tensile strength and heat distortion temperature and have not improved overall toughness.
It is an objective of the present invention to provide HIPS and ABS polyblends having improved elongation at fail without loss of tensile strength giving improved overall toughness by the blending of liquid polymers of conjugated diene monomers in the polyblend.
It is also an objective of this invention to provide HIPS and ABS polyblends having improved elongation at fail that can be prepared by polymerization processes wherein the incorporation of a liquid polymer of a conjugated diene monomer in the polymerizing composition does not inhibit the polymerization process and provides a compatible additive for the rubber phase of the polyblend that improves elongation at fail and low temperature properties without loss of tensile strength or heat distortion temperature of the polymeric polyblend.
These and other objectives and advantages of the present invention will become evident from the following summary, detailed description and claims of the invention.